The present invention relates to pulsed hypersonic compression waves and more particularly to shaped charge devices using pulsed hypersonic compression waves to create thrust.
In propulsion devices such as jet engines and rocket engines, propulsion thrust is obtained by high-speed exhaust flows. Conventional jet engines obtain the high-speed exhaust by combustion products of fuel and air, while rocket engines obtain the high-speed exhaust by internal combustion products of fuel and oxidizer. The high pressure combustion products are forced through a restrictive orifice, or nozzle, to obtain the high-speed exhaust flow.
Several problems are inherent in the conventional systems. The combustion in both jet and rocket engines must contain extremely high internal pressures and are therefore limited by constriction material strength. As the internal combustion pressure increases, the combustion chamber wall must increase in thickness to contain the pressure, increasing the combustion chamber weight proportionally and limiting the design. Also, as the exhaust nozzle diameter is reduced to increase exhaust speed, cooling the engine and nozzle becomes increasingly more difficult. In addition, pulsed engines are unable to evacuate the combustion products in a short time moment, thus limiting the firing speed.
Furthermore, as internal pressure in the combustion chamber increases, higher fuel and oxidizer inlet pressures are required to introduce fuel and oxidizer into the combustion chamber, requiring heavier weight pumps that operate at higher horsepower. One example of such limitations on present engines is seen in the phase two main space shuttle engine. The engine requires 108,400 horsepower to drive the fuel and oxidizer pumps alone. Inlet pressures exceed 6,800 psi in order to obtain an internal combustion chamber pressure to only 3,260 psi with a combustion chamber to nozzle ratio of 77 to 1.
The huge plume of fire trailing the shuttle and other rockets is caused by incomplete combustion of the fuel and oxidizer prior to exiting the exhaust nozzle. The fuel and oxidizer igniting outside the engine provide virtually no thrust and are thus wasted. The above space shuttle engine example requires 2,000 pounds of fuel and oxidizer per second to obtain 418,000 pounds thrust at sea level. Furthermore, the continuous ignition of present engines causes high heat transfer to engine parts, particularly the nozzle orifice, and the high heat transfer requires the use of costly exotic materials and intricate cooling schemes to preserve the engine structure.
Prior efforts to improve the engine design focus on various components, including the nozzle. For example, U.S. Pat. No. 6,003,301 to Bratkovich et al., entitled xe2x80x9cExhaust Nozzle for Multi-Tube Detonative Enginesxe2x80x9d teaches the use of a nozzle in an engine having multiple combustor tubes and a common plenum communicating with the combustor tubes. Accordingly, Bratkovich et al. teach that the common plenum and a compound flow throat cooperate to maintain a predetermined upstream combustor pressure regardless of downstream pressure exiting the expansion section.
While the prior art addresses many aspects of propulsion devices, it does not teach the use of a shaped charge in a jet or rocket engine. A shaped charge is generally defined as a charge that is shaped in a manner that concentrates its explosive force in a particular direction. While the general theory behind shaped charges has been known for many years, the prior art has restricted the use of shaped charges to warheads and certain other expendable detonation devices. In a typical warhead, the shaped charge directs its explosive forces forwardly, in the direction the warhead is traveling, by igniting moments before or substantially simultaneously with impact. The highly concentrated force can be used to create a cheap, lightweight armor-piercing device. Examples of shaped charge devices are described in U.S. Pat. No. 5,275,355 to Grosswendt, et al., entitled xe2x80x9cAntitank Weapon For Combating a Tank From The Top,xe2x80x9d and U.S. Pat. No. 5,363,766 to Brandon, et al., entitled, xe2x80x9cRamjet Powered, Armor Piercing, High Explosive Projectile.xe2x80x9d Shaped charges in such devices are not used to provide propulsion.
Similarly, current engines configured to drive a turbine do not employ shaped charge engines. One example of a pulsed turbine engine is disclosed in U.S. Pat. No. 6,000,214 to Scragg, entitled xe2x80x9cDetonation Cycle Gas Turbine Engine System Having Intermittent Fuel and Air Delivery.xe2x80x9d Scragg teaches a detonation cycle gas turbine engine including a turbine rotor within a housing. Valveless combustion chambers are positioned on either side of the rotor to direct combustion gases toward the turbine blades. The two combustion chambers alternately ignite the mixture of fuel and oxidizer to cyclically drive the turbine. While Scragg discloses a useful engine, efficiency, horsepower per unit of engine weight, and other performance parameters could be greatly improved. For example, the Scragg device constructed to deliver 200 hp would require a 560 cubic inch combustion chamber and would weigh 262 pounds, while a 200 hp engine using a shaped charge as in the present invention would require a combustion chamber of only 18 cubic inches and would weigh only 70 lbs.
There is therefore a need for a shaped charge propulsion device that provides substantially improved performance than prior art devices.
The present invention provides a shaped charge engine that overcomes many limitations of the prior art. The apparatus includes a blast-forming chamber comprising an inner annular charge forming housing having a conical convex projection that forms the inner walls of the blast-forming chamber. A central through hole is provided to allow exhaust gases to exit. An outer housing comprises a generally round disk with an inner conical concave depression and through holes for the insertion of fuel and ignition. The two housings are joined by conventional means such as welding or bolts. The resulting chamber formed by joining the two housings is taper-conical in shape, wider at the base, and gradually decreasing in cross-sectional area as it rises to the apex. This construction forms a circular pinch point or throat toward the apex that forms the primary or first stage compression area. A secondary compression zone is created at the apex of the outer housing, just beyond the throat. Hypersonic gases exit the through hole in the inner housing.
In accordance with further aspects of the invention, a directed thrust is formed in a pulsed manner using a contained bum that starts at a peripheral base area and is directed in a tapered-conical shape that forms a primary compression area adjacent the apex of the conical shape. The compressed bum thereafter continues to the apex of the tapered-conical shape, creating a high-speed convergence or secondary compression zone before being exhausted. This construction provides a more complete ignition within the chamber, enhancing efficiency by capturing more of the energy before it leaves the engine. It also allows for the combustion products to exit the primary combustion chamber more rapidly, thus allowing a higher pulse rate of firing while maintaining the high compression exhaust flows by not compressing exhaust products to final velocity internally.
In accordance with other aspects of the invention, the engine includes a sensor to determine the ambient air density, allowing the engine to selectively consume air or oxidizers, as appropriate.
In accordance with still further aspects of the invention, inexpensive conventional fuels, such as gasoline, acetylene, butane, propane, natural gas, and diesel oil are mixed with air or an oxidizer into a combustible mixture and infused under positive pressure into the hollow blast-forming chamber in a manner that permits positive shutoff between a series of induction cycles to accommodate ignition cycles.
In accordance with yet other aspects of the invention, an igniter ignites the combustible mixture initiating a blast wave or pulse at the base of the hollow blast-forming chamber. As the blast wave or pulse advances into a gradually compressed blast-forming chamber, additional mass may be injected into the blast chamber, thereby increasing the momentum of the blast wave. Explosion products are compressed by the gradually decreasing cross sectional area of the blast-forming chamber. The increasing pressure drives the blast wave into a primary compression zone formed by an annular restriction between the truncated end of a central conical projection and an opposing truncated hemispherical or domed inner surface of the outer housing.
Compression of the blast wave into this annular restriction creates a high-speed radial flow of explosion products toward the center of the truncated hemispherical or domed surface. The opposing high-speed radial streams of explosion products converge at the center of the truncated hemispherical or domed surface creating a secondary zone of increased compression of the explosion products. Confluence of mass and kinetic energy in the secondary compression zone forms the explosion products into hypersonic gases that exit in a controlled blast directed through an exhaust port centrally located at the apex of the central conical projection. The resulting high pressure hypersonic exhaust is expelled in a directed blast from the exhaust port without the need for an exit nozzle.
In accordance with still another aspect of the invention, the exit velocity of the combustion products and ejecta is controlled by increasing or decreasing the size, length, diameter, and depth angle of the blast chamber, and adjusting fuel-oxidizer mixtures.
In accordance with still further aspects of the invention, the controlled blasts formed in the blast-forming chamber are repeatable by the serial infusion and ignition of additional charges of the combustible mixture. Furthermore, in repeating pulsed modes, the blast power and frequency are throttle controllable by increasing or decreasing the flow rate of the combustible mixture or adjusting the cycle rate independently of the mixture flow rate.
In accordance with yet another aspect of the invention, the engine is operated in a pulsed mode along a continuum between an aerobic or air-breathing jet mode and an anaerobic or non-air-breathing rocket mode. Accordingly, fuel is mixed with air, oxidizer, or any combination of the two in any relative concentration. The relative concentrations of air and oxidizer in the combustible mixture is dynamically adjusted into a blend of air and oxidizer, which may be a function of oxygen concentration in the ambient atmosphere.
In accordance with further aspects of the invention, the particular geometry of the shaped charge engine may be varied, while still retaining the inventive aspects, including primary and secondary convergence zones. Accordingly, the cross-sectional shape may be annular, square, rectangular, triangular, or a variety of other forms depending on the desired results and the space available to house the engine in the vehicle to be propelled.
In accordance with still further aspects of the invention, the exhaust gases collide at a secondary convergence zone to create hypersonic exhaust. The opposing streams of gases may originate in chambers that are substantially opposite one another and at least partially orthogonal to the direction of travel. Alternatively, the blast chamber may be configured such that the explosive products travel in an acute or an obtuse angle with respect to the direction of travel before reaching the throat and the secondary compression zone.
In accordance with additional aspects of the invention, the angle at which the exhaust gases converge may be dynamically controlled during operation of the engine. The generally opposed sides of the generally annular blast-forming chamber may be hinged to allow the chambers to be moved fore and aft to adjust the angle of convergence.
In accordance with yet other aspects of the invention, the cross-sectional area of the throat or pinch point may be increased or decreased. By decreasing the size of the throat area, the exhaust gases travel at a higher velocity, creating a relative spike in the exhaust velocity and therefore the thrust. Conversely, by increasing the throat size, the exhaust gases exit more uniformly and at a lower relative velocity.
In accordance with other aspects of the invention, the engine may be used to provide direct thrust to propel a rocket, aircraft, personal water craft, or other vehicle.
In accordance with still other aspects of the invention, the exhaust gases created by the engine may be used to drive a turbine that is used to propel the vehicle. In such an embodiment, the engine may, for example, be used to power a car.
In accordance with still further aspects of the invention, the pressure, exhaust, pulse, or heat produced by the shaped charge engine may be used in a wide variety of applications, including, for example, vehicle propulsion, pest control, demolition, cutting tools, etching tools, heating tools, spraying tools, high-speed guns, generators, boilers, and closed-system pressure devices.